Message-ID: <54EEE90A.8070906@ti.com>
Date:	Thu, 26 Feb 2015 11:36:10 +0200
From:	Roger Quadros <rogerq@...com>
To:	zhangfei <zhangfei.gao@...aro.org>, <balbi@...com>
CC:	Kishon Vijay Abraham I <kishon@...com>, <mark.rutland@....com>,
	Peter Chen <peter.chen@...escale.com>,
	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	"dan . zhao" <dan.zhao@...ilicon.com>,
	Wangbinghui <wangbinghui@...ilicon.com>,
	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<devicetree@...r.kernel.org>, <linux-usb@...r.kernel.org>
Subject: Re: [PATCH v4 4/4] phy: add phy-hi6220-usb

Zhangfei,

On 26/02/15 10:48, zhangfei wrote:
> Hi, Roger
> 
> On 02/24/2015 06:13 PM, Roger Quadros wrote:
>>>> On Sat, Feb 21, 2015 at 11:03:05PM +0800, zhangfei wrote:
>>>>>>>>> +static void hi6220_start_peripheral(struct hi6220_priv *priv, bool on)
>>>>>>>>> +{
>>>>>>>>> +    struct usb_otg *otg = priv->phy.otg;
>>>>>>>>> +
>>>>>>>>> +    if (!otg->gadget)
>>>>>>>>> +        return;
>>>>>>>>> +
>>>>>>>>> +    if (on)
>>>>>>>>> +        usb_gadget_connect(otg->gadget);
>>>>>>>>> +    else
>>>>>>>>> +        usb_gadget_disconnect(otg->gadget);
>>>>>>>>
>>>>>>>> why is the PHY fiddling with pullups ?
>>>>>>>
>>>>>>> We use this to enable/disable otg gadget mode.
>>>>>>
>>>>>> I got that, but the pullups don't belong to the PHY, they belong to the
>>>>>> gadget.
>>>>>>
>>>>>>> The gpio_id & gpio_vbus are used to distinguish otg gadget mode or
>>>>>>> host mode.
>>>>>>> When micro usb or otg device attached to otg, gpio_vbus falling down.
>>>>>>> And gpio_id = 1 is micro usb, gpio_id = 0 is otg device.
>>>>>>
>>>>>> all of that I understood clearly :-)
>>>>>>
>>>>>>> So when micro usb attached, we enable gadget mode; while micro usb
>>>>>>> detached, we disable gadget mode, and dwc2 will automatically set to
>>>>>>> host mode.
>>>>>>
>>>>>> that's all fine, I'm concerned about letting the PHY fiddle with
>>>>>> something it doesn't own. If I am to change pullups rules in udc-core,
>>>>>> this is likely to break down miserably and I don't want to have to go
>>>>>> through that.
>>>>>
>>>>> Thanks for the clarifying.
>>>>
>>>> no problem.
>>>>
>>>>> How about using usb_gadget_vbus_connect/disconnect, which are used in many
>>>>> files under drivers/usb/phy.
>>>>> There is no vbus_session in dwc2/gadget.c, I thought it would be same as
>>>>> pullup.
>>>>>
>>>>> However, usb_gadget_vbus_connect still need para gadget, where should we put
>>>>> this file, drivers/usb/phy or drivers/phy
>>>>
>>>> drivers/phy, if the framework misses anything you need, it's a great
>>>> opportunity to give back to the community by extending the framework.
>>>
>>> Sorry, I am a little confused.
>>> I need some concrete suggestion for the next step of this patch, which is required for the community board, hikey board.
>>>
>>> Do you mean in the future we need use hsotg->phy instead of hsotg->uphy.
>>>          struct phy *phy;
>>>          struct usb_phy *uphy;
>>> usb_phy has many members that struct phy does not have, including otg.
>>> struct usb_otg          *otg;
>>> Is that mean we need port such member from usb_phy to phy.
>>
>> In my opinion otg structure should belong to the USB core part that takes care
>> of the OTG/DRD state machine. We still don't have a clear solution here and
>> I'm currently investigating this.
>> My current work is to get Dual role functionality working with DWC3 controller and TI
>> platforms.
>>
>> Currently phy drivers take care of OTG operation themselves but there is an opportunity
>> to share code and centralize USB role switching.
>> The USB core should be the owner of the Host controller, Gadget controller and the OTG phy
>> and should take care of the that.
> 
> Good idea.
> If you have any patch, I will be very happy to verify.

Not yet. but expect some RFC patches in a few days.

> 
> How about adding these things in drivers/phy/phy-core.c, it is also sharable, though not in usb core.

Not the best place IMO. Kishon can give his views if he sees it as a temporary solution.

> 
> Just tried adding one member struct usb_otg otg to struct phy, since not find any good member can hold usb_otg.
> In drivers/phy/phy-core.c, adding extcon_register_interest, phy_vbus_notifier, phy_set_peripheral, it works for me, dwc2 on hikey board.

cool.

> 
>>
>>>
>>> Besides, are you ok with using usb_gadget_vbus_connect/disconnect.
>>
>> I don't think PHY is the right place for this even though older drivers seem to be doing so.
>> But at the same time there is nowhere else to add this at the moment.
>> The right place should be the USB core that is aware of host/gadget, phy and the state of the bus.
> 
> Understand.
> 
>>>> Scratching one's own itch kinda thing...
>>>>
>>>>>>>>> +static void hi6220_detect_work(struct work_struct *work)
>>>>>>>>> +{
>>>>>>>>> +    struct hi6220_priv *priv =
>>>>>>>>> +        container_of(work, struct hi6220_priv, work.work);
>>>>>>>>> +    int gpio_id, gpio_vbus;
>>>>>>>>> +    enum usb_otg_state state;
>>>>>>>>> +
>>>>>>>>> +    if (!gpio_is_valid(priv->gpio_id) || !gpio_is_valid(priv->gpio_vbus))
>>>>>>>>> +        return;
>>>>>>>>> +
>>>>>>>>> +    gpio_id = gpio_get_value_cansleep(priv->gpio_id);
>>>>>>>>> +    gpio_vbus = gpio_get_value_cansleep(priv->gpio_vbus);
>>>>>>>>
>>>>>>>> looks like this should be using extcon
>>>>>>> Not used extcon before.
>>>>>>> However, we need gpio_vbus interrupt.
>>>>>>> Checked phy-tahvo.c and phy-omap-otg.c, not find extcon related with
>>>>>>> interrupt.
>>>>>>> Will investigate tomorrow.
>>>>>>
>>>>>> drivers/extcon/extcon-gpio.c
>>>>> I think there is no need to use extcon, gpio is clear enough.
>>>>> extcon-gpio.c even do not support dt.
>>>>
>>>> well, add DT. The whole idea of free software is that we improve on
>>>> things we already have. EXTCON is *the* API to handle such things.
>>>
>>
>> I wrote the extcon-gpio-usb.c driver for exactly your use case. It is
>> queued for v4.1
>> https://lkml.org/lkml/2015/2/2/187
> 
> That's great, thanks.
>>
>> It takes care of debouncing for you. Although currently it supports only ID gpio,
>> it should be very easy to extend to VBUS sense GPIO.
>>
>>> I think I am still not understanding extcon-gpio, not sure why need use this API here.
>>
>> several reasons. Let me list a few.
>> 1) Code reuse. Every PHY driver doesn't need to implement GPIO/interrupt handling and debouncing.
>> It just registers what cable events it wants to hear and gets a notification.
>> 2) The events (ID/VBUS) are not only interesting for the PHY driver but also the controller
>> driver and the OTG state machine (whenever it exists at a common place) ;).
>> 3) standardization because of common API.
> 
> Thanks for the explanation.

no problem :).

cheers,
-roger
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